This invention relates generally to exercise equipment and more specifically to exercise devices which strengthen the abdominal muscles (the Rectus Abdominous, The Internal and External Obliques and the Transverse Abdominous), and the lower back muscles.
In general, a muscle is strongest at its mid-range of motion. When human beings stand up straight, the muscles of the torso at the center section of the body, which hold the body upright, are in their strongest position, and allow for functional movement bending forward and backward. Most abdominal exercise programs work the abdominal motions from a flat floor. This only brings into play one half of the motion of the muscles, leaving a large weakness in the muscle itself that could develop into numerous back and hip problems.
The abdominal muscles can work or bend the spine over a range from 30.degree. extension back through center, or the neutral position, to 25.degree. flexion forward of the neutral position. The function of the abdominal muscles is to bend the spine. The abdominal muscles are in four segments, each of which corresponds to a vertebrae on the back. Therefore, when the top abdominal segment contracts, it bends the third and fifth thoracic vertebrae with a pivot point between them. Then when the second abdominal segment contracts, it bends the fifth and sixth thoracic vertebrae and the pivot point moves down between them and so on, until we reach full spinal flexion.
A device for strengthening the abdominal muscles is disclosed in U.S. Pat. No. 4,372,553 (Hatfield). The device comprises a bench with a curved back on which the exerciser sits. A harness is attached to the shoulders of the exerciser with a cable holding weights so that when the exerciser pulls down, he or she is working against the weight resistance. This device is not fully effective in exercising the abdominal muscles because the hip flexures can do most of the work in pulling the torso forward and down, rather than the abdominal muscles. In addition, the Hatfield device does not provide any exercise for the lower abdominal or the lower back muscles.
Another device for exercising the abdominal muscles is disclosed in U.S. Pat. No. 4,752,067 (Colonello). This device comprises a specially shaped cradle-like basin with hand grips. The basin is shaped so that it can rock back and forth. Because the rocking motion is obtained by pulling the body up using the arms, again, the abdominal muscles do not do the full work with regard to extension and flexion. Additionally, the device does not cause abdominal muscles to move through their full range of motion nor does it provide exercise for the lower abdominal muscles or the back muscles.
There is a need for an exercise device which exercises the abdominal muscles over their full range of motion, which makes the abdominal muscles work fully, and which exercises the lower abdominal muscle and the lower back muscles as well as the upper abdominal muscles.